How Long Does it Take a 20 Gallon Water Heater to Replenish Itself?

Motor homes and camping trailers usually only have a 20-gallon hot water heater.

Hot water heaters have two ratings, the first-hour rating and the recovery rating. The first-hour rating or draw efficiency indicates how much hot water is available during the most demanding hours of the day. The recovery rating refers to the unit's ability to replenish hot water as cold water is pulled into the tank; that rating is given in gallons per hour. The type of heating element affects these measurements and the length of time it takes to heat the water in the tank.

Recovery Rating

A 20-gallon hot water heater tank, typically found in motor homes and camping trailers, has recovery rates that vary based on whether the fuel is propane, gas or oil. With a 90-degree Fahrenheit rise -- the standard temperature differential that it takes to raise the temperature of cold water -- a 20-gallon electric tank has a recovery rate of 7.5 gallons per hour and a draw efficiency of 14 gallons. Draw efficiency relates to the number of gallons available during peak usage based on 70 percent of the tank's overall size. It takes a little more than an hour for the electric 20-gallon hot water tank to completely replenish itself.